Fix some clang-tidy findings

    * modernize-use-std-numbers
    * modernize-use-starts-ends-with

verible/verilog/analysis/checkers/truncated-numeric-literal-rule.cc

diff --git a/verible/verilog/analysis/checkers/truncated-numeric-literal-rule.cc b/verible/verilog/analysis/checkers/truncated-numeric-literal-rule.cc
index 298bc6c..c6a17c2 100644
--- a/verible/verilog/analysis/checkers/truncated-numeric-literal-rule.cc
+++ b/verible/verilog/analysis/checkers/truncated-numeric-literal-rule.cc
@@ -18,6 +18,7 @@
 #include <cctype>
 #include <cmath>
 #include <cstddef>
+#include <numbers>
 #include <set>
 #include <string>
 #include <string_view>
@@ -136,11 +137,13 @@
       // without fully parsing the decimal number ?
       double v;
       if (absl::SimpleAtod(literal, &v) && !std::isinf(v)) {
-        return std::max(129, static_cast<int>(ceil(log(v) / log(2))));
+        return std::max(129,
+                        static_cast<int>(ceil(log(v) / std::numbers::ln2)));
       }
 
       // Uh, more than 300-ish decimal digits ? ... rough estimation it is.
-      return ceil((literal.length() - 1) * log(10) / log(2));
+      return ceil((literal.length() - 1) * std::numbers::ln10 /
+                  std::numbers::ln2);
     } break;
     default:
       break;  // unexpected base

verible/verilog/formatting/token-annotator.cc

diff --git a/verible/verilog/formatting/token-annotator.cc b/verible/verilog/formatting/token-annotator.cc
index fc6d2f0..6b42b60 100644
--- a/verible/verilog/formatting/token-annotator.cc
+++ b/verible/verilog/formatting/token-annotator.cc
@@ -263,8 +263,7 @@
   // If a closing ')', that ends the definition name.
   if (left.TokenEnum() == verilog_tokentype::PP_Identifier &&
       right.TokenEnum() == verilog_tokentype::PP_define_body &&
-      right.Text().substr(0, 2) == "``" &&
-      right.OriginalLeadingSpaces().empty()) {
+      right.Text().starts_with("``") && right.OriginalLeadingSpaces().empty()) {
     return {0, "Preserve spacing in concatenated name"};
   }